JP2001121736A - Image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image-forming apparatus to which a resolution enhancement to meet a change with time is applied. SOLUTION: In this image-forming apparatus which scans a plurality of laser beams thereby printing image data, an image correction device is set for detecting a pattern to be corrected from the input image data and correcting the pattern. The pattern is changed by a control signal from the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for printing image data by simultaneously scanning a plurality of laser beams.

[0002]

2. Description of the Related Art In recent years, a laser printer using electrophotography has been used for an output device of a computer, an output unit of a facsimile, or a so-called digital copying machine for printing image data read from an image scanner.

[0003] Laser printers are of the digital type,
The print quality greatly depends on the resolution. When the resolution is low, image defects such as jagged oblique lines become noticeable. In order to obtain a high-quality image, 300 to 600 dpi (dots / inch) is considered as one standard as a necessary resolution.

[0004] An increase in the resolution of an input image directly leads to an increase in the load at the time of image processing, so that the resolution cannot be increased unnecessarily. Therefore, there is resolution enhancement as a technique for improving the resolution by estimating (without increasing the resolution of the image) from an image having a small amount of information.

[0005] The most typical method among the resolution enhancement methods is a method using template matching. The template matching method scans a pattern of a target pixel (pixel at the center position of the template) and its surrounding pixels, compares the pattern with a prepared pattern (template pattern), and sets the target pixel according to the result. This is a method of determining the print size and position of the image.

[0006] As a conventional technique for performing such resolution enhancement, there are Japanese Patent No. 2797224 and Japanese Patent No. 2886192.

Incidentally, in order to increase the speed of a laser printer, it is necessary to scan a laser beam at high speed in the main scanning direction and the sub-scanning direction. Specifically, the rotating polygon mirror is rotated at a high speed in the main scanning direction, and the photoconductor is rotated at a high speed in the sub-scanning direction.

However, a laser beam (laser light)
The rotation speed of the rotating polygon mirror that deflects the light is close to the limit. For this reason, instead of increasing the rotation speed of the rotary polygon mirror, a multi-beam method of simultaneously scanning a plurality of laser beams is employed. As described above, the laser printer often employs the multi-beam scanning method in order to perform high-speed printing.

[0009]

When the resolution is enhanced by the above-described high-speed laser printer, since the template pattern is set in advance, if the image quality of the laser printer changes due to aging or the like, it cannot respond to the image quality change. There was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus to which resolution enhancement capable of coping with aging is applied.

[0011]

In order to achieve the above object, the present invention provides an image forming apparatus for printing image data by scanning a plurality of laser beams to detect a pattern to be corrected from input image data. And an image correction device for correcting the pattern, and changing the pattern to be corrected by an external control signal.

Further, a line memory group for expanding image data corresponding to a plurality of laser beams into image data of a plurality of lines is detected and matched with a template pattern prepared in advance from the image data of the plurality of lines. A template matching group that outputs data, a template matching group operation control circuit that controls the operation of the template matching group, and modulated image data that sets the print size and position of the pixel of interest in the template from the matching data. An image correction device is provided which includes a modulation circuit for outputting, a modulation operation control circuit for controlling the operation of the modulation circuit, and a delay adjustment circuit for adjusting a delay time of the modulated image data.

The present invention further comprises the template matching group operation control circuit for generating a template matching operation control signal for adding or deleting a template pattern according to a parameter reflecting a change in image quality.

[0014] Further, there is provided the modulation operation control circuit for generating a modulation operation control signal for changing a modulation pattern according to a parameter reflecting a change in image quality.

Further, the parameters reflecting the image quality change are provided with the template matching operation control circuit and the modulation operation control circuit, which are count values for counting the number of printed sheets.

According to the present invention, since the operation of the template matching group or the operation of the modulation circuit is controlled by the number of prints as a parameter reflecting the change in image quality, an image forming apparatus to which resolution enhancement capable of coping with aging is applied. Can be provided.

[0017]

FIG. 2 shows an embodiment of the present invention.

In FIG. 2, image data D 1 created by a host computer (personal computer) 1 is input to a printer controller 2. Image data D1
Is created by a user using input means (not shown) of the host computer 1. The image data D1 will be described as page description data indicating the content of the page to be recorded.

The image data D1 output from the host computer 1 is transmitted to the printer controller 2 via a network (not shown).

The printer controller 2 expands the image data D1 which is page description data transmitted from the host computer 1 for each page, and converts the image data D1 into raster image data D2 which is an array of two-dimensional image data.
Output to

The printer controller 2 outputs the number of prints 40 to the image correction device 3.

The image correction device 3 is provided with a raster image data D2
From the comparison with the pattern (template pattern) prepared in advance by template matching,
Modulated image data D6 for setting the print size and position of the pixel of interest in the template is output according to the result.

The image correction device 3 adds or deletes a template pattern and modulates image data D6 for setting a print size and a position of a pixel of interest in the template according to the number of prints 40 input from the printer controller 2. Add or delete the modulation pattern that is the basis of.

Here, the laser printer 4 employs a two-beam scanning system for simultaneously scanning two laser beams.

The laser printer 4 outputs the modulated image data D6
Is formed on a recording sheet as a print image.

FIG. 1 is a block diagram of the image correction device 3 shown in FIG.

The line memory group 5 stores raster image data D
2 is developed into a plurality of lines of image data D3.

The template matching group 6 compares the image data D3 of a plurality of lines with a previously prepared pattern (template pattern) by template matching set by the template matching operation control signal 43, and outputs matching data D4. I do.

The modulation circuit 7 outputs, from the matching data D4, modulated image data D5 for setting a print size and a position of a target pixel in the template according to the modulation pattern set by the modulation operation control signal 44.

The delay adjusting circuit 8 adjusts the delay time of the modulated image data D5 and outputs image data D6.

Template matching operation control circuit 41
Is the number of prints 4 input from the printer controller 2
By means of 0, a template matching operation control signal 43 for adding or deleting a template pattern of the template matching group 6 is generated. The modulation operation control circuit 42
A modulation operation control signal 44 for adding or deleting the modulation pattern of the modulation circuit 7 is generated based on the number of prints 40 input from the printer controller 2.

FIG. 3 is an example of the laser printer 4 shown in FIG.

When the image data D6 is input to the laser printer 4, the laser beam generating circuit 9 generates a laser beam 10 by the laser beam generating circuit 9. The laser printer 4 includes a charger 12, a developing device 13, and a transfer device 14 around a photoconductor 11,
The surface of the photoreceptor 11 is uniformly charged by the charger 12, exposed by the laser beam 10, toner is adhered by the developing device 13, the toner is transferred to the recording paper 15 by the transfer device 14, and the recording paper is The printed image is obtained on the recording paper 15 by fusing the toner to the recording paper 15.

FIG. 4 shows an example of the line memory group 5 shown in FIG.

The line memory group 5 includes line memories 17 to 2
0, and the raster image data D2, that is, the multi-beam scanning method in which the laser printer 4 scans two laser beams simultaneously, converts the two raster image data D2-1 and D2-2 into six lines. The image data is developed into image data D3, that is, D3-1 to D3-6. Here, the image data D3-1 to D3-6 of six lines are developed by setting the template size of the template matching 6 to 5 × 5.
Is assumed.

FIG. 5 shows an example of the template matching group 6 shown in FIG.

The template matching group 6 includes first to fourth template matchings 21 to 24. The five lines of image data input to the first template matching 21 and the second template matching 22 are D
3-1 to D3-5, and five lines of image data input to the third template matching 23 and the fourth template matching 24 are D3-2 to D3-6.
According to the template pattern set by the template matching operation control signal 43, the first to fourth template matchings 21 to 24 are made up of six lines of image data D
3 with the first to fourth matching data D4-1 to D4-
Convert to 4.

FIG. 6 shows an example of the modulation circuit 7 shown in FIG.

The modulation circuit 7 comprises first to fourth PWM (pulse width modulation) circuits 25 to 28. Depending on the modulation pattern set by the modulation operation control signal 44, the first to fourth
PWM (pulse width modulation) circuits 25 to 28 convert the first to fourth matching data D4-1 to D4-4 into first to fourth matching data.
Are converted into modulated image data D5-1 to D5-4. FIG.
Is an example of the delay adjustment circuit 8 shown in FIG.

The delay adjusting circuit 8 comprises first to fourth delay circuits 29 to 32. First to fourth delay circuits 29 to 3
2 is the first to fourth modulated image data D5-1 to D5-2
To the first to fourth image data D6-1 to D6-
2 is output.

FIG. 8 shows an example of the laser beam generating circuit 9 shown in FIG. The laser beam generation circuit 9 includes first to fourth LD (laser diode) drivers 33 to 36 and first and second LDs 37 to 38. The output current I1 of the first LD driver 33 and the output current I2 of the second LD driver 34 are added and supplied to the first LD 37. The output current I3 of the third LD driver 35 and the fourth LD driver 36 Are added and supplied to the second LD 38. That is, the first and second image data D6-
1 to D6-2, the first LD 37 emits light, and the third LD 37 emits light.
To the fourth image data D6-3 to D6-4.
LD emits light.

FIG. 9 is an example of the template matching operation control circuit 41 shown in FIG. The template matching operation control circuit 41 includes an LUT (lookup table) 45. The LUT 45 converts the number of prints 40 into a template matching operation control signal 43.

FIG. 10 is an example of the modulation operation control circuit 42 shown in FIG. The modulation operation control circuit 42 includes an LUT
(Lookup table) 46. LUT46
Converts the number of prints 40 into a modulation operation control signal 43.

FIG. 11 is an example of the template matching 21 shown in FIG. Template matching 21
Is composed of a matrix register 47, a template matching A48, a template matching B49, a template matching C50, and an encoder 51. The matrix register 47 stores five lines of image data D3-1 to D3-1.
D3-5 is developed in a matrix of 5 × 5 pixels. The template matching A48, the template matching B49, and the template matching C50 have different template patterns, respectively.
Whether to operate or not is determined. The encoder 51 encodes template matching A48, template matching B49, and template matching C50, and outputs respective matching data D4-1 (2
Bit).

FIG. 12 is an example of the PWM 25 shown in FIG. The PWM 25 includes a pulse generation unit 48 and a pulse selection unit 49. The pulse generator 48 generates a multi-stage pulse group 50 having a pulse width equal to or smaller than the pulse width of one pixel. The pulse selector 49 outputs the matching data D4-1.
And the modulation operation control signal 44, the multi-stage pulse group 50
And outputs it as modulated image data D5-1.

FIG. 13 is a timing chart showing the operation of the image correction device 3 of FIG.

The LUT 45 of FIG. 9 outputs a template matching operation control signal 43 so that the template pattern of the template matching A shown in FIG. 11 is as shown in FIG. Suppose you

When the six lines of image data D3-1 to D3-6 output from the line memory group 5 shown in FIG. 4 are as shown in FIGS. The matching data D4-1 of the matched first template matching 21 and the matching data D4-3 of the third template matching 23 become "2" as shown in (g) and (i). Second template matching 2
Since other template patterns are set in the second and fourth template matchings 24, the image pattern in FIG. 9 does not match each template pattern, and the matching data D4-2 and D4-4 are (h), ( "0" or "1" is output as in j). First PWM shown in FIG.
25 and the third PWM 27 output the modulated image data D5-1 and D5-3 having a pulse width of t9 when the matching data D4-1 and D4-3 are "2", so that (k) and (m)
become that way. The second PWM 26 and the fourth PWM 28
Since the matching data D4-2 and D4-4 are "1", the same modulated image data as the image data (c) and (d) is output as shown in (l) and (n).

When the modulated image data (k) to (n) are output, delays are generated for the input image data as shown at t1 to t4. The delay adjustment circuit 8 shown in FIG. 7 performs image data D6-1 and D6-2 of (o) and (p).
, And the image data D6-3 and D6-4 of (q) and (r) are in phase with each other, so that delays t5 to t6 are generated.

The image data D6-1 to D6-4 are (o)
When the current is supplied to the first to fourth LD drivers 33 to 36 shown in FIG. 8 as shown in (r) to (r), the current I5 supplied to the first LD 37 is changed to the second LD 38 as shown in (s). Is supplied as shown in (t).

The first LD 37 emits light by the current I5 of (s), and the second LD 38 emits light by the current I6 of (t).

FIG. 15 shows the number of prints 40, the template matching 21 shown in FIG. 11, and the PW shown in FIG.
It is a figure showing the relation of M25. It is assumed that the print quality changes when the number of prints 40 becomes n. If the number of prints 40 is less than n, the template matching A and the template matching B operate and the template matching C
Does not work. When the number of prints 40 exceeds n, the operation of template matching A does not change, but the pulse width of the corresponding modulated image data D5 changes from PW1 to PW2. On the other hand, the template matching B changes to not operate, and the template matching C changes to operate.

As described above, depending on the number of prints 40,
Add or delete template patterns to be detected.
Since the pulse width of the modulated image data is changed, it is possible to cope with a change in print quality due to a change over time.

In the above-described embodiment, depending on the number of prints,
Although the addition and deletion of the template pattern to be automatically detected and the change of the pulse width of the modulated image data are performed, the change may be manually performed by monitoring the change of the print image quality.

[0055]

As described above, according to the present invention,
Since the detected template pattern is added or deleted depending on the number of prints, and the pulse width of the modulated image data is changed, it is possible to cope with a change in print image quality due to aging.

[Brief description of the drawings]

FIG. 1 is a block diagram of the image correction device shown in FIG. 2;

FIG. 2 is an embodiment of the present invention.

FIG. 3 is an example of the laser printer 4 shown in FIG.

FIG. 4 is an example of a line memory group 5 shown in FIG. 1;

FIG. 5 is an example of a template matching group 6 shown in FIG.

FIG. 6 is an example of a modulation circuit 7 shown in FIG.

FIG. 7 is an example of a delay adjustment circuit 8 shown in FIG. 1;

8 is an example of the laser beam generation circuit 9 shown in FIG.

FIG. 9 is an example of a template matching operation control circuit 41 shown in FIG. 1;

FIG. 10 is an example of a modulation operation control circuit 42 shown in FIG. 1;

11 is an example of the template matching 21 shown in FIG.

FIG. 12 is an example of the PWM 25 shown in FIG. 6;

FIG. 13 is a time chart for explaining the operation of the image correction device 3 of FIG. 1;

FIG. 14 shows a template matching A4 shown in FIG. 11;
8 is a template pattern.

FIG. 15 is a diagram showing the relationship between the number of prints 40, the template matching 21 shown in FIG. 11, and the PWM 25 shown in FIG.

[Explanation of symbols]

3 image correction device, 5 line memory group, 6 template matching group, 7 modulation circuit, 8 delay adjustment circuit,
9: laser beam generation circuit, 33 to 36: LD driver, 37 to 38: LD, 40: number of prints, 41: template matching operation control circuit, 42: modulation operation control circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Kobayashi 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Masaki Masuchi 2-6-Otemachi, Chiyoda-ku, Tokyo No. 2 Nippon Koki Co., Ltd. (72) Tadashi Kitai 2-6-2 Otemachi, Chiyoda-ku, Tokyo F-term (in reference) 2C362 BA56 BA66 CB02 CB37 CB43 CB74 CB75

Claims (5)

[Claims] An image forming apparatus for printing image data by scanning a plurality of laser beams is provided with an image correction device for detecting and correcting a pattern to be corrected from input image data, and for externally outputting the pattern to be corrected. An image forming apparatus characterized in that it is changed by a control signal from the image forming apparatus. 2. An image correction apparatus comprising: a line memory group for expanding image data corresponding to a plurality of laser beams into a plurality of lines of image data; and a template pattern prepared in advance from the plurality of lines of image data. A template matching group that detects a match and outputs matching data, a template matching group operation control circuit that controls the operation of the template matching group,
A modulation circuit that outputs modulated image data for setting a print size and a position of a pixel of interest in a template from the matching data, a modulation operation control circuit that controls an operation of the modulation circuit, and a delay of the modulated image data. The image forming apparatus according to claim 1, further comprising: a delay adjusting circuit that adjusts time. 3. The template matching group operation control circuit generates a template matching operation control signal for adding or deleting a template pattern according to a parameter reflecting a change in image quality.
The image forming apparatus as described in the above. 4. The image forming apparatus according to claim 2, wherein the modulation operation control circuit generates a modulation operation control signal for changing a modulation pattern according to a parameter reflecting a change in image quality. 5. The image forming apparatus according to claim 3, wherein the parameter reflecting the image quality change is a count value for counting the number of printed sheets.